Holden's major internal conflict revolves around his inability to deal with the death of his younger brother Allie. Holden looked up to Allie's good nature, and when he died, Holden was sorry that his parents lost their better son. Holden's parents never got him any counseling or professional help, so Holden's feelings of loss and inadequacy eat at him from the inside. Because he is dealing with this internal conflict, Holden lashes out at others causing external conflicts. For example, Holden gets into a fight with Stradlater because Stradlater does not respect Holden's memories of Allie which Holden wrote about in the essay. Holden does not try to understand anyone else, and this causes external conflicts in his life.
Holden's inability to deal with things, is his most pressing conflict that he has. He lives in the past and therefore, can't move on with his life. He is an angry young man. His external conflicts stem from this. He is angry with life, and society. He thinks people are hypocrites and that they only care about material things. He will start fights with people for no reason at all. He is very selfish at this point in his life. It is quite apparent that he is suffering from some sort of mental break, and this is causing him to create external conflict with everyone he meets.
Holden's biggest internal conflict, is that he can not deal with the death of his younger brother, Allie. This event has haunted him since his death. Holden slept in the garage the night his brother died and broke all the windows in the garage. He has harbored this anger and sadness inside himself for many years, now. He is unprepared on how to deal with is feelings.
"The thing was, I couldn't think of a room or a house or anything to describe the way Stradater said he had to have. I'm not too crazy about describing rooms and houses anyway. So what I did, I wrote about my brother Allie's baseball mitt. It was a very descriptive subject. It really was. He was left handed. The thing that was descriptive about it, though, was that he had poems written all over the fingers and the pocket and everywhere. In green ink. He wrote them on it so that he'd have something to read when he was in the field and nobody was at bat. He's dead now. He got leukemia and died when we were up in Maine, on July 18, 1946. You'd have liked him. He was two years younger than I was, but he was about fifty times as intelligent. He was terrifically intelligent. His teachers were always writing letters to my mother, telling her what a pleasure it was having a boy like Allie in their class. And they weren't just shooting the crap. They really meant it. But it wasn't just that he was the most intelligent member in the family. He was also the nicest, in lots of ways. He never got mad at anybody...God he was a nice kid, though."
As you can see, Holden is not capable of letting go of the past. He lives constantly trying to tell himself how wonderful things were, but in reality things were not great. Holden's inability to face his future with confidence creates conflict where ever he goes.